Ethylene and its copolymers are important items of commerce. The copolymerization of ethylene with alpha, omega-dienes in many instances, such as with Ziegler-Natta and metallocene type catalysts, yields crosslinked polymers since both of the olefinic bonds in the diene may be polymerized by these catalysts. Indeed to make polyolefins (including polyethylenes) having branches containing olefinic bonds, nonconjugated external-internal diolefins such as 1,4-hexadiene (or other types of dienes having two olefinic groups of differing reactivities) must be used.
It has now been found that selected iron or cobalt complexes of a 2,6-pyridinecarboxaldehydebis(imines) or 2,6-diacylpyridinebis(imines) may be used to copolymerize ethylene and various dienes, and that the resulting copolymers contain branches having terminal olefin groups. In some instances part of the diene which is incorporated into the copolymer is present as a saturated cyclic structure which is part of the polymer main chain.
U.S. Pat. No. 5,955,555, WO99/12981, WO99/46302, WO99/46303, WO99/46304, WO99/46308, WO99/50318 (corresponding to U.S. patent application Ser. No. 09/273,409, filed Mar. 22, 1999, now U.S. Pat. No. 6,214,761), WO99/62963 (corresponding to U.S. patent application Ser. No. 09/317,104, filed May 21, 1999, now U.S. Pat. No. 6,252,022), WO99/62967 (corresponding to U.S. patent application Ser. No. 09/317,563, filed May 21, 1999, now abandoned), WO00/15646, WO00/24788, WO00/32641 and WO00/50470 (all of which are incorporated by reference herein for all purposes as if fully set forth) describe the use of selected iron or cobalt complexes of a 2,6-pyridinecarboxaldehydebis(imine) or a 2,6-diacylpyridinebis(imine) as polymerization catalysts for ethylene and other olefins. No mention is made of the use of dienes as comonomers.